Purpose: Suction is achieved when complete dentures are first fitted, but it fades during
the months following insertion, when it is increasingly complemented by muscular
denture control. The aim of this study was therefore to investigate the extent to which
patterns of mastication are altered by experimental failure of physical retention. Materials
and Methods: Seven edentulous volunteers had maxillary replica dentures made, with
fine tubes incorporated so that alternating positive and negative air pressure could be
generated under the fitting surface. Mandibular movements, EMG, and pressure under the
denture base were recorded during unilateral chewing. Results: The change of physical
retention passed undetected by all subjects; they continued chewing apparently
undisturbed. However, during air injection, the mandibular excursions were slightly
slower (nonsignificant) and demonstrated a reduced variance (P ¡Ü .05). The muscle
activity showed significantly longer bursts (P ¡Ü .05), and peak activity occurred later in
the cycle (nonsignificant). Conclusion: Sudden failure of denture retention seems to
initiate an immediate and effective modulation of centrally generated muscular activity
patterns.

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